The optimization of phycoerythrin extraction from Porphyra haitanensis were investigated by single experiments and response surface methodology. The single experiments were used to explore the effects on the extraction rate and purity of phycoerythrin by different enzyme amount, ultrasonic time, ultrasonic power, pH and solid-liquid ratio. The best pH and solid-liquid ratio were determined as 5.0 and 140 (g/mL), respectively. Meanwhile, the enzyme amount, ultrasonic time and ultrasonic power were investigated through response surface experiment. The optimal extraction conditions were determined as follows: enzyme amount 0.05 g, ultrasonic time 40 min and ultrasonic power 90% of the rated one. Under these conditions, the extraction rate and purity of phycoerythrin were reached (1.808±0.007)% and 0.460±0.001, respectively.